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Desmond J Tobin, Full Professor of Dermatological Science & Director, University College Dublin

As with any complex multicellular tissue system, the hair follicle and scalp are prone to broadly similar underlying processes that determine the functional longevity of organs and tissues. No matter how complex the tissue system is, it will contain cells that eventually lose functionality, reproductive potential and will ultimately die. The hair follicle is somewhat unusual among mammalian tissues in that it is a veritable histologic mélange of multiple cell types (eg epithelial, mesenchymal and neuro-ectodermal) that function contemporaneously in all stages of their life histories (eg stem cells, transient-amplifying cells, and terminally-differentiating cells). Some of these interactive cell systems appear to be non-essential for overall hair follicle survival (eg melanocytes). However, strikingly greying hair follicles may grow even more vigorously than their pigmented predecessors. Moreover, the hair follicle is unique in the adult mammal in that it follows a tightly-regulated script of multiple life-long cycles of cellular birth, proliferation, differentiation and death. Powerful evolutionary selection ensures that the hair follicle is, in the main, hardwired against significant aging-related loss of function, even after 12 or more decades of life - although some would argue with this view, if only on purely cosmetic grounds. Processes underlying aging in general (eg oxidative damage, telomere shortening, age-relating deficiencies related to nuclear/mitochondrial DNA damage and repair as well as age-related reductions in the cells’ energy supply) will all impact on whether some follicular cell subpopulations will enter cellular senescence. For most, hair loss shows an increasing incidence with age; in men - male pattern-balding (androgenetic alopecia) driven by androgens, and in women - female pattern hair loss with a more general, diffuse hair thinning. The rapidly growing hair follicle is exposed to a substantial number of extrinsic and intrinsic stressors and sits deep within the dermis of the scalp with its bulb residing in the hypodermis. Recently research suggests detrimental age-related changes in the surrounding scalp skin may perturb the hair follicle growth environment. In that sense scalp skin aging and hair follicle aging may show parallel trajectories. In this presentation I will present evidence of age-related changes in human adult scalp skin and comment on how these changes may contribute to the aging hair phenotype.

Dr Desmond J. Tobin is Full Professor of Dermatological Science and Director of The Charles Institute of Dermatology at the UCD School of Medicine, Dublin. Prior to Sept 2018 he was Professor of Cell Biology and Director of the Centre for Skin Sciences at the University of Bradford (UK). He holds a BSc from the National University of Ireland (Maynooth), a PhD from the University of London (St. John’s Institute of Dermatology) and post-doctoral training from New York University Medical School’s Dept. of Dermatology. Over the past 25 years he has researched in basic and applied skin/hair sciences, with a focus on the biology of human melanocytes/pigmentation and hair growth disorders, especially those with an immune basis. Des is a Fellow of the Royal College of Pathologists, Royal Society of Biology, Institute of Trichologists (Vice-President), and Institute of Biomedical Science. He is the immediate past president of the British Society for Investigative Dermatology, and member of the UK Translational Network in Dermatology (UKTREND). Des serves(ed) on several editorial boards, scientific advisory panels, and the UK-based Research Excellent Framework REF2021. He has published over 150 publications, incl. 3 books. His H-Index (Google Scholar) is 74 (Jan 2021), reflecting the top 5-10% of world scientists. 


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